This invention relates to amorphous alloys for a magnetic head core and a magnetic head using same, and more particularly it deals with a magnetic head of high performance and prolonged service life including a part formed of amorphous alloy materials, for video equipment.
Heretofore, alloy materials, such as ferrite materials including Mn-Zn ferrite and Sen-alloy, have been in use as materials for forming magnetic heads. These materials are not considered ideal materials for producing magnetic heads. For example, Mn-Zn ferrite has high permeability in high frequency region but tends to develop distortion during recording because of low saturation magnetic flux density and to produce noise during playback because of high magnetostriction. Sen-alloy has a high saturation magnetic flux density and a low magnetostriction. However, owing to its low permeability in high frequency region, it has the disadvantage of being low in playback efficiency. In magnetic heads of the prior art, attempts have been made to eliminate the defects of the material as much as possible by optimizing the structure design. However, their performance has been far from being ideal. Magnetic tapes that have hitherto been widely in use have raised no serious problems in practical use because they are relatively low in coercive force.
In order to improve recording density to increase the performance of equipment and obtain a compact size in video equipment, metal powder tape of high coercive force has recently been developed and already used for audio equipment. It is assumed that it will be put to practical use for video equipment in the near future. Research that has been conducted shows that difficulties would be encountered in making the best use of the characteristics of the metal powder tape by combining the magnetic head of ferrite material of the prior art with the metal powder tape of high coercive force because of poor performance of the magnetic heads of ferrite material.
Amorphous magnetic alloys have in recent years been discovered. They have excellent characteristics as materials for magnetic heads, and it is generally expected that they will prove ideal materials for producing heads. Amorphous alloys, which are characterized in that the atoms constituting them are not arranged in an orderly manner with a long range order as in crystals but in what is referred to as a vitreous state in which they are in frozen liquid condition, are expected to show unique properties lacked in materials of the prior art.
Research conducted by us has shown that not all the amorphous alloys have excellent characteristics that render them suitable for use as materials for producing magnetic heads and that materials of specific dimensions of such alloys that are limited in composition can be used for producing magnetic heads. Particularly, it has been revealed that only the magnetic heads of special design compatible with the specific use exhibit much better performance than magnetic heads of the prior art.
For example, as shown in Japanese Patent Application Laid-Open Publication No. 91014/74, it is possible to produce amorphous alloys of a very wide range of components in composition. However, the majority of such alloys are low in saturated magnetic flux density and not suitable for forming magnetic heads. Also, the majority of such alloys show deterioration in characteristics due to the stress applied thereto during the process of forming same into magnetic heads even if they exhibit excellent magnetic characteristics as materials. Amorphous alloys tend to have magnetic after-effect due to the instability of their structure, even if they do not much suffer the aforesaid disadvantages. Thus it has hitherto been believed that it is impossible to put amorphous alloys into practical use as materials for producing magnetic heads.
As described in Japanese Patent Application Laid-Open Publication No. 94211/76, magnetic heads formed of amorphous alloys are known. However, the magnetic heads formed of such novel materials could not exhibit better performance than magnetic heads formed of materials of the prior art unless they have a special head construction.
The following references are cited to show the state of the art: (i) Japanese Patent Application Laid-Open Publication No. 91014/74; (ii) Japanese Patent Application Laid-Open Publication No. 65395/76; and (iii) Japanese Patent Application Laid-Open Publication No. 94211/76.